This is not her first stint with Marvel. She contributed to a bi-weekly series called Black Panther: Long Live the King, and wrote Wakanda Forever. She also counts the director of the LGBT love ...
The implication appears to be that going forward, M'Baku will rule as king of Wakanda, while Shuri will still be Black Panther, and he's presumably seeking the throne with her permission.
Marvel Clad in distinctive bullet-proof black armour, usually capeless but with a full facemask, Black Panther - or T'Challa - is the king and protector ... that has been a long time coming.